With use of a cellular immunoabsorbent technique we plan to continue investigations which permit the quantitative separation of peripheral blood, lymph node or splenic lymphocytes into immunoglobulin-bearing T and Null cells. With these isolated populations of cells we intend to concentrate further on defining subpopulations of each and investigate their specificity and participation in interactions of cellular immune and antibody dependent immune responses. These studies should provide increased understanding of the mechanism and nature of the genetic control of the immune response, the mechanism by which cells cooperate, and the nature of the regulatory or suppressor effects of cell subpopulations.